Yes, that was exactly the issue–there is an “Ultimate Category Excluder” plugin (I was not the one who set up this blog or any of the plugins). I just deleted the plugin because I don’t have a need for it. Thanks so much for the help!
@schulte – It was not a Sticky Post, but I did change it to just the Massage Chairs category and it worked, so thank you! Now my next question – how can I make sure those other categories are not excluded from the Loop? I don’t know anything about that, but from a brief search before it looks a little complicated to work with. Is there a simple way to fix that?